Process for producing tyres, tyres thus obtained and elastomeric compositions used therein

ABSTRACT

A crosslinkable elastomeric composition includes at least one elastomeric polymer including carboxylic groups, and at least one epoxidized elastomeric polymer including greater than or equal to 0.1 mol % and less than or equal to 20 mol % of epoxide groups relative to a total number of moles of monomers present in the at least one epoxidized elastomeric polymer. The composition is crosslinkable in a substantial absence of additional crosslinking agents. A tyre for vehicles includes a carcass structure, a belt structure extended coaxially around the carcass structure, and a tread band extended coaxially around the belt structure. The tread band comprises an external rolling surface intended to come into contact with the ground. In one embodiment of the present invention, the tread band includes at least one crosslinked elastomeric material. A process for producing the tyre is also disclosed.

The present invention relates to a process for producing tyres forvehicle wheels, to the tyres thus obtained and to the crosslinkableelastomeric compositions used therein. More particularly, the presentinvention relates to a process for producing tyres for vehicle wheels,which can be carried out in the substantial absence of conventionalcrosslinking agents, to the tyres thus obtained and to the crosslinkablecompositions used therein.

Processes for vulcanizing diene elastomers with sulphur are widely usedin the rubber industry for the production of a wide range of products,and in particular tyres for vehicle wheels. Although these processesgive high-quality vulcanized products, they are considerably complicatedto carry out, mainly due to the fact that, in order to obtain optimumvulcanization within industrially acceptable times, it is necessary touse a complex vulcanizing system which includes, besides sulphur orsulphur-donating compounds, one or more activators (for example stearicacid, zinc oxide and the like) and one or more accelerators (for examplethiazoles, dithiocarbamates, thiurams, guanidines, sulphenamides and thelike). The presence of these products can, in some cases, entailconsiderable problems in terms of the harmfulness/toxicity both duringproduction and during use, in particular when the vulcanized productsare intended for medical/health-care or food use. In addition, it isknown that the use of sulphur or sulphur-donating compounds leads,during the vulcanization stage which is generally carried out attemperatures above 150° C., to the development of volatile sulphurizedcompounds.

Consequently, in recent years, research efforts have been directed alongtwo different lines, the first being to improve the known vulcanizationprocesses in order to make them more efficient and cleaner, the secondaimed at developing alternative crosslinking techniques. Althoughappreciable progress has been made, it is not possible to state at thepresent time that alternative techniques to crosslinking with sulphurexist which would give similar results and would simultaneously affordan effective simplification in terms of production. For example,crosslinking processes via peroxide compounds require specialprecautions on account of the instability of these compounds, inaddition to requiring the use of activators. Crosslinking by means ofradiation involves the use of complex equipment, as well as theincorporation of all the precautions required when high-energy andhigh-power radiation is used.

So-called “self-crosslinking” elastomeric compositions, i.e.compositions which do not require the use of crosslinking agents such assulphur or sulphur compounds, are known in the art.

For example, U.S. Pat. No. 2,724,707 describes elastomeric compositionsconsisting of a diene polymer containing carboxylic groups, inparticular a carboxylated nitrile rubber (XNBR) obtained by partialhydrolysis of a butadiene/acrylonitrile polymer, in which a polyvalentmetal oxide (for example zinc oxide) is dispersed. On heating thesecompositions, they crosslink according to a mechanism of ionic type.

A study of the crosslinking of XNBR with a high degree of carboxylation,by reaction with an epoxy resin (for example bisphenol A diglycidylether) in the presence of reinforcing fillers such as carbon black,silica and clay, is reported in the article by S. K. Chakraborty and S.K. De, published in the Journal of Applied Polymer Science, Vol. 27, pp.4561-4576 (1982). The crosslinking is carried out by heating thecompound to 150°-180° C. As is known, epoxy resins are low molecularweight products in which the epoxide (or oxirane) groups are “external”,i.e. they are located in a terminal position on the main hydrocarbonchain, the oxygen atom forming the oxirane ring being linked to both thelast and the penultimate carbon atoms of this chain.

A study of the crosslinking of a composition based on epoxidized naturalrubber (ENR) and XNBR is reported in the article by R. Alex, P. P. De,N. M. Mathew and S. K. De, published in Plastics and Rubber Processingand Applications, Vol. 14, No. 4, 1990. In particular, this articledescribes the crosslinking of compositions consisting of ENR and XNBR assuch or containing silica or carbon black as reinforcing filler.According to what reported by the authors, the crosslinking reaction inthe ENR and XNBR mixtures comprises the formation of ester bonds betweenthe epoxide groups and carboxylic groups. The rheometric curves wouldshow absence of reversion, stability of the crosslinked structure and ahigh rate of crosslinking.

Italian patent IT 1,245,551 describes self-crosslinking compositionscontaining an epoxidized elastomer and a crosslinking agent of formulaR1—R—R2, in which R is an arylene, alkylene or alkenylene group, whileR1 and R2 are carboxylic, amine, sulphonic or chlorosulphonic groups.Dicarboxylic or polycarboxylic acids, or mixtures thereof, can be usedas crosslinking agents. Self-crosslinking compositions containing anepoxidized elastomer and a second elastomer in which the repeating unitsof the polymer chain contain at least one carboxylic group are alsodescribed. For example, self-crosslinking compositions are obtained bymixing an epoxidized elastomer (for example the products ENR 25 or ENR50 which are available under the brand name Epoxyprene® from GuthrieSymington Ltd.) with a butadiene/acrylic acid copolymer (for example aproduct sold by Polysar/Bayer under the brand name Krynac®). Thecrosslinking reaction takes place by heating between the epoxide groupsand the carboxylic groups, with formation of ester bonds.

U.S. Pat. No. 5,173,557 describes self-vulcanizing compositionscomprising an elastomeric polymer functionalized with isocyanate groupsand a compound containing at least two active hydrogens of Zerewitinofftype, or self-crosslinking compositions comprising an elastomericpolymer containing active hydrogens of zerewitinoff type and a compoundcontaining at least two isocyanate groups. Alternatively, an elastomericpolymer containing either isocyanate groups or active hydrogens ofZerewitinoff type can be used, without using an additional crosslinkingagent. The active hydrogens can be present, for example, on hydroxide,amine, carboxylic or thiol groups. In order to avoid undesiredpre-crosslinking of the elastomer, the isocyanate groups are blockedbeforehand with suitable functional groups, which are removed by heatingbefore the crosslinking reaction between the free isocyanate groups andthe active hydrogens, optionally with the aid of a catalyst.

On the basis of the Applicant's experience, the self-crosslinkingcompositions proposed hitherto in the prior art do not provide a validalternative to conventional compositions vulcanized with sulphur orderivatives thereof. The reason for this is that the performancequalities of the crosslinked products are generally unsatisfactory, inparticular for applications such as tyre compounds, in which asubstantial consistency of the elastic performance qualities over a widerange of working temperatures and at the same time high abrasionresistance without unacceptably increasing the hardness is required.This is the case, for example, for the self-crosslinking compositionsdescribed above in which a polymer containing carboxylic groups (forexample XNBR). is hot-crosslinked in admixture with an epoxidizedelastomeric polymer or with an epoxy resin.

The Applicant has now found that crosslinked products, and in particulartyres for vehicle wheels, which have the desired combination ofproperties can be produced in the substantial absence of additionalcrosslinking agents, by using self-crosslinking compositions comprisinga mixture of an elastomeric polymer containing carboxylic groups and anepoxidized elastomeric polymer containing from 0.1 mol % to 20 mol % ofepoxide groups relative to the total number of moles of monomers presentin the polymer.

After heating, these compositions achieve a high degree of crosslinkingwithout addition of conventional crosslinking agents, with crosslinkingtimes contained within limits which are acceptable for industrial use.The resulting crosslinked product combines excellent mechanical andelastic performance qualities (in particular stress at break, elongationat break, modulus and hardness) which are such as to make theself-crosslinking compositions above particularly suitable aselastomeric materials to be used for the production of tyres, inparticular tread bands.

According to a first aspect, the present invention thus relates to aprocess for producing tyres for vehicle wheels, said process comprisingthe following stages:

manufacturing a green tyre comprising at least one crosslinkableelastomeric material; subjecting the green tyre to moulding in a mouldcavity defined in a vulcanization mould;

crosslinking the elastomeric material by heating the tyre to apredetermined temperature and for a predetermined time;

characterized in that the crosslinkable elastomeric material comprises:(a) an elastomeric polymer containing carboxylic groups, (b) anepoxidized elastomeric polymer containing from 0.1 mol % to 20 mol % ofepoxide groups relative to the total number of moles of monomers presentin the polymer, in which said crosslinking stage is carried out in thesubstantial absence of additional crosslinking agents.

According to a preferred aspect, the crosslinkable elastomeric materialmay comprise a lubricant, preferably an epoxidized lubricant containingepoxide groups located internally on the molecule.

According to another preferred aspect, the crosslinking stage is carriedout by heating the crosslinkable elastomeric material to a temperatureof at least 120° C. for a time of at least 3 minutes, preferably to atemperature of from 130° C. to 230° C. for a time of from 5 to 90minutes.

In accordance with a particularly preferred aspect, said crosslinkableelastomeric material also comprises a reinforcing filler.

In a second aspect, the present invention relates to a tyre for vehicleswheels, comprising one or more components made of crosslinkedelastomeric material, characterized in that at least one of saidcomponents comprises, as crosslinked elastomeric material, anelastomeric polymer containing carboxylic groups and an epoxidizedelastomeric polymer containing from 0.1 mol % to 20 mol % of epoxidegroups relative to the total number of moles of monomers present in thepolymer, said polymers being crosslinked in the substantial absence ofadditional crosslinking agents.

According to a preferred aspect, the crosslinkable elastomeric materialmay comprise a lubricant, preferably an epoxidized lubricant containingepoxide groups located internally on the molecule.

According to a further aspect, the present invention relates to a tyrefor vehicles, comprising a belt structure extended coaxially around acarcass structure and a tread band extended coaxially around the beltstructure and having an external rolling surface which is intended tocome into contact with the ground, characterized in that said tread bandcomprises an elastomeric polymer containing carboxylic groups and an.epoxidized elastomeric polymer containing from 0.1 mol % to 20 mol % ofepoxide groups relative to the total number of moles of monomers presentin the polymer, said polymers being crosslinked in the substantialabsence of additional crosslinking agents.

According to a preferred aspect, the crosslinkable elastomeric materialmay comprise a lubricant, preferably an epoxidized lubricant containingepoxide groups located internally on the molecule.

According to a further aspect, the present invention relates to acrosslinkable elastomeric composition comprising: (a) an elastomericpolymer containing carboxylic groups; and (b) an epoxidized elastomericpolymer containing from 0.1 mol % to 20 mol % of epoxide groups relativeto the total number of moles of monomers present in the polymer; saidcomposition being crosslinkable in the substantial absence of additionalcrosslinking agents.

According to a preferred aspect, said composition may comprise alubricant, preferably an epoxidized lubricant containing epoxide groupslocated internally on the molecule.

According to a further aspect, the present invention relates to acrosslinked elastomeric product obtained by crosslinking a crosslinkablecomposition as defined above.

For the purposes of the present description and the claims, theexpression “in the substantial absence of additional crosslinkingagents” means that the crosslinkable composition is not subjected to theaction of other systems capable of bringing about its crosslinking, orthat other products which may be present in the composition can inthemselves participate in the crosslinking reaction, but are used inamounts less than the minimum amount required to obtain an appreciabledegree of crosslinking in short times (for example within 5 minutes). Inparticular, the compositions according to the present invention arecrosslinkable in the substantial absence of the crosslinking systemscommonly used in the art, such as, for example, sulphur or sulphurdonors, peroxides or other radical initiators, and neither are thesecompositions subjected to the action of high-energy radiation (UV, gammarays, etc.) such as to induce crosslinking phenomena in the polymer

The elastomeric polymers containing carboxylic or epoxide groups (whichare also referred to hereinbelow for simplicity as “carboxylatedelastomeric polymers” and “epoxidized elastomeric polymers”) which maybe used in accordance with the present invention are homopolymers orcopolymers with elastomeric properties, having a glass transitiontemperature (T_(g)) of less than 23° C. and preferably less than 0° C.The carboxylated elastomeric polymers may generally contain at least 0.1mol %, preferably from 1 mol % to 30 mol %, more preferably from 2 mol %to 20 mol %, of carboxylic groups relative to the total number of molesof monomers present in the polymer. The epoxidized elastomeric polymersgenerally contain from 0.1 mol % to 20 mol %, preferably from 0.5 mol %to 15 mol %, more preferably from 1 mol % to 10 mol %, of epoxide groupsrelative to the total number of moles of monomers present in thepolymer. Blends of various polymers containing carboxylic or epoxidegroups, or alternatively blends of one or more carboxylated orepoxidized polymers with one or more non-functionalized elastomericpolymers, also fall within the present definition.

Both for the carboxylated copolymers and for the epoxidized copolymers,.the structure can have a random, blocked, grafted or mixed structure.The average molecular weight of the polymer is preferably between 2,000and 1,000,000, preferably between 50,000 and 500,000.

Epoxidized or carboxylated diene homopolymers or copolymers in which thebase polymer structure, of synthetic or natural origin, is derived fromone or more conjugated diene monomers, optionally copolymerized withmonovinylarenes and/or polar comonomers, are particularly preferred.Preferably, the base polymer structure is derived from the(co)polymerization of diene monomers containing from 4 to 12, preferablyfrom 4 to 8, carbon atoms, chosen, for example, from: 1,3-butadiene,isoprene, 2,3-dimethyl-1,3-butadiene, 3-butyl-1,3-octadiene,2-phenyl-1,3-butadiene, and the like, or mixtures thereof. 1,3-Butadieneand isoprene are particularly preferred.

Monovinylarenes which can optionally be used as comonomers generallycontain from 8 to 20, preferably from 8 to 12, carbon atoms and can bechosen, for example, from: styrene; 1-vinylnaphthalene;2-vinylnaphthalene; various alkyl, cycloalkyl, aryl, alkylaryl orarylalkyl derivatives of styrene, such as, for example: 3-methylstyrene,4-propylstyrene, 4-cyclohexylstyrene, 4-dodecylstyrene,2-ethyl-4-benzylstyrene, 4-p-tolylstyrene, 4-(4-phenylbutyl)styrene, andthe like, or mixtures thereof. Styrene is particularly preferred. Thesemonovinylarenes can optionally be substituted with one or morefunctional groups, such as alkoxy groups, for example 4-methoxystyrene,amino groups, for example 4-dimethylaminostyrene, and the like.

Various polar comonomers can be introduced into the base polymerstructure, in particular vinylpyridine, vinylquinoline, acrylic andalkylacrylic acid esters, nitriles and the like, or mixtures thereof,such as, for example: methyl acrylate, ethyl acrylate, methylmethacrylate, ethyl methacrylate, acrylonitrile.

Among the base polymer structures which are particularly preferred are:natural rubber, polybutadiene, polyisoprene, styrene/butadienecopolymers, butadiene/isoprene copolymers, styrene/isoprene copolymers,butadiene/acrylonitrile copolymers, nitrile rubbers, or mixturesthereof.

In the case of base structures of copolymer type, the amount of dienecomonomer relative to the other comonomers is such as to ensure that thefinal polymer has elastomeric properties. In this sense, it is notpossible generally to establish the minimum amount of diene comonomerrequired to obtain the desired elastomeric properties. As an indication,an amount of diene comonomer of at least 50% by weight relative to thetotal weight of the comonomers can generally be considered sufficient.

The preparation of the base polymer can be carried out according toknown techniques, generally by (co)polymerization of the correspondingmonomers in emulsion, in suspension or in solution.

To introduce carboxylic groups, to obtain carboxylated elastomericpolymers, the base polymer thus obtained can be made to react with acarboxylating agent in the presence of a radical initiator, preferablyan organic peroxide (for example dicumyl peroxide or benzoyl peroxide).Carboxylating agents commonly used are, for example: maleic anhydride,itaconic anhydride, thioglycblic acid, beta-mercaptopropionic acid, andthe like.

Further information regarding the structure and the processes forproducing carboxylated elastomers are given, for example, in the articleby H. P. Brown in Rubber Chemistry and Technology, Vol. XXX, 5, page1347 et seq (1957) or in U.S. Pat. No. 2,724,707.

The epoxidation to obtain epoxidized elastomeric polymers is carried outaccording to known techniques, for example by reaction in solution withan epoxidizing agent. This agent is generally a peroxide or a peracid,for example m-chloroperbenzoic acid or peracetic acid, and the like, orhydrogen peroxide in the presence of a carboxylic acid or a derivativethereof, for example acetic acid or acetic anhydride and the like,optionally mixed with an acid catalyst such as sulphuric acid. Moredetails regarding processes for epoxidizing elastomeric polymers aredisclosed, for example, in U.S. Pat. No. 4,341,672 or by Schulz et al.in Rubber Chemistry and Technology, Vol. 55, p. 809 et seq.

The introduction of carboxylic or epoxide groups can also be carried outduring the synthesis of the polymer by copolymerization of a conjugateddiene, optionally mixed with monovinylarenes and/or polar comonomers, asreported above, and an olefinic comonomer containing, respectively, oneor more carboxylic or epoxide groups, or derivatives thereof.

Carboxylated olefinic comonomers that are usually used are, for example:acrylic acid, methacrylic acid, sorbic acid, beta-acryloxypropanoicacid, ethacrylic acid, 2-ethyl-3-propylacrylic acid, vinylacrylic acid,itaconic acid, cinnamic acid, maleic acid, fumaric acid, and the like,or mixtures thereof.

Within this class of carboxylated elastomeric polymers, particularlypreferred are: 1,3-butadiene/(meth)acrylic acid copolymers,1,3-butadiene/acrylonitrile/(meth)acrylic acid copolymers,1,3-butadiene/styrene/(meth)acrylic acid copolymers, and the like, ormixtures thereof.

Alternatively, in the case of carboxylated polymers the correspondingcarboxylic derivatives may be used, in particular anhydrides, esters,nitriles or amides. In the latter case, the polymer obtained is thensubjected to hydrolysis so as to partially or totally convert thefunctional groups thus introduced into free carboxylic groups.

Olefinic comonomers containing epoxide groups may be chosen, forexample, from: glycidyl acrylate, glycidyl methacrylate,vinylcyclohexene monoxide, allyl glycidyl ether and methallyl glycidylether. The introduction of the epoxide groups via the abovementionedepoxidized comonomers may be carried out by copolymerization of thecorresponding monomers according to known techniques, in particular byradical-mediated emulsion copolymerization.

Other carboxylated or epoxidized elastomeric polymers which may be usedare elastomeric copolymers of one or more monoolefins with an olefiniccomonomer containing one or more carboxylic or epoxide groups orderivatives thereof. The monoolefins can be chosen from: ethylene andalfa-olefins generally containing from 3 to 12 carbon atoms, such as,for example: propylene, 1-butene, 1-pentene, 1-hexene, 1-octene and thelike, or mixtures thereof. The following are preferred: copolymers ofethylene and an alfa-olefin, and optionally a diene; homopolymers ofisobutene or copolymers thereof with small amounts of a diene, which areoptionally at least partially halogenated. The diene optionally presentcontains, in general, from 4 to 20 carbon atoms, and is preferablychosen from: 1,3-butadiene, isoprene, 1,4-hexadiene, 1,4-cyclohexadiene,5-ethylidene-2-norbornene, 5-methylene-2-norbornene, and the like. Amongthese, the following are particularly preferred: ethylene/propylenecopolymers (EPR) or ethylene/propylene/diene copolymers (EPDM);polyisobutene; butyl rubbers; halobutyl rubbers, in particularchlorobutyl or bromobutyl rubbers; and the like, or mixtures thereof.

Olefinic comonomers containing epoxide or carboxyl groups may be chosenfrom those mentioned above for the diene polymers.

When a diene comonomer is present, it may be used to introducecarboxylic or epoxide groups by means of a carboxylation or epoxidationreaction, respectively, as described above.

In accordance with the present invention, the carboxylated elastomericpolymer is generally present in amounts of from 10 to 90 phr (phr=partsby weight per 100 parts of polymer base), preferably from 25 to 85 phr,and the epoxidized elastomeric polymer is generally present in an amountof from 10 to 90 phr, preferably from 15 to 75 phr.

The crosslinkable compositions according to the present invention cancontain reinforcing fillers, in amounts generally of between 10 and 120phr, preferably from 30 to 100 phr. The reinforcing filler may be chosenfrom those commonly used for crosslinked products, and in particular fortyres, such as: carbon black, silica, alumina, aluminosilicates, calciumcarbonate, kaolin, and the like, or mixtures thereof.

The crosslinkable compositions according to the present invention cancomprise other commonly used additives chosen on the basis of thespecific application for which they are intended. For example, thefollowing can be added to these compositions: antioxidants, protectiveagents, plasticizers, compatibilizing agents for the reinforcing filler,adhesives, anti-ozone agents, modifying resins., fibres (for exampleKevlar® pulp), and the like.

In particular, for the purpose of further improving the processability,a lubricant can be added to the crosslinkable compositions according tothe present invention, this lubricant being chosen in general frommineral oils, vegetable oils, synthetic oils and the like, or mixturesthereof, for example: aromatic oil, naphthenic oil, soybean oil, and thelike. Polar lubicants, for example phthalates and polyesters, areparticularly preferred.

Epoxidized lubricants may also be used, in particular lubricantscontaining epoxide groups located internally on the molecule (which arereferred to for simplicity hereinbelow as “organic compounds withinternal epoxide groups” or “epoxidized organic compounds”). These areproducts of hydrocarbon type which are in the form of oils or viscousliquids at room temperature.

Said lubricants contain at least two internal epoxide groups, i.e.groups in which an oxirane bridge links:

(i) two adjacent carbon atoms located on the main chain, with thecondition that neither of said two adjacent carbon atoms is a terminalcarbon atom of the chain; or

(ii) two adjacent carbon atoms located on a side chain.

However, the presence of internal epoxide groups does not exclude thepossibility of the molecule also having epoxide groups in a terminalposition.

At least two internal epoxide groups are present in the preferredlubricants according to the present invention. In general, the amount ofepoxide groups is such that the epoxide equivalent weight of theepoxidized compound is usually between 40 and 2,000, preferably between5.0 and 1,500, more preferably between 100 and 1,000. The term “epoxideequivalent weight” (EEW) means the molecular weight of the epoxidizedcompound per mole of oxirane oxygen, or:${EEW} = \frac{1600}{\%\quad O}$where %O is the content of oxirane oxygen, expressed as a percentage byweight of oxirane oxygen relative to the total weight of the compound.The content of oxirane oxygen in the epoxidized compounds can bedetermined according to known techniques, for example by titration witha solution of hydrobromic acid in acetic acid.

One class of polar lubricants containing internal epoxide groups whichare particularly preferred is that of epoxidized oils, which can beobtained by epoxidation of unsaturated fatty acids or esters (inparticular glycerides, diglycerides or triglycerides) of unsaturatedfatty acids, of synthetic or natural origin, or alternatively byepoxidation of mixtures of said unsaturated acids or esters withsaturated fatty acids or esters thereof. The saturated or unsaturatedfatty acids generally contain from 10 to 26 carbon atoms, preferablyfrom 14 to 22 carbon atoms. Examples of unsaturated fatty acids are:myristoleic acid, palmitoleic acid, oleic acid, gadoleic acid, erucicacid, ricinoleic acid, linoleic acid, linolenic acid, arachidonic acid,and the like, or mixtures thereof. Examples of saturated fatty acidsare: lauric acid, myristic acid, palmitic acid, stearic acid, behenicacid, and the like, or mixtures thereof. Epoxidized vegetable oils suchas, for example: epoxidized linseed oil, epoxidized safflower oil,epoxidized soybean oil, epoxidized corn oil, epoxidized cottonseed oil,epoxidized rapeseed oil, epoxidized castor oil, epoxidized tung oil,epoxidized tall oil, octyl epoxytallate, epoxidized sunflower oil,epoxidized olive oil, and the like, or mixtures thereof, areparticularly preferred. The epoxidized oils generally have a freezingtemperature of less than 23° C., preferably less than 10° C. Products ofthis type can be found on the market, for example, under the brand namesEpoxol® (FACI, American Chemical Service Inc.); Paraplex®, Plasthall®and Monoplex® (C. P. Hall); Vikoflex® and Ecepox® (Elf Atochem).

Another class of lubricants containing internal epoxide groups which canbe used advantageously according to the present invention consists ofepoxidized diene oligomers, in which the base polymer structure, ofsynthetic or natural origin, is derived from one or more conjugateddiene monomers, optionally copolymerized with other monomers containingethylenic unsaturation. These oligomers generally have an averagemolecular weight (number-average), which can be determined, for example,by gel permeation chromatography (GPC), of between 500 and 10,000,preferably between 1,000 and 8,000.

Oligomers derived from the (co)polymerization of conjugated dienemonomers containing from 4 to 12, preferably from 4 to 8, carbon atoms,chosen, for example, from: 1,3-butadiene, isoprene, chloroprene,2,3-dimethyl-1,3-butadiene, 3-butyl-1,3-octadiene,2-phenyl-1,3-butadiene, and the like, or mixtures thereof, areparticularly preferred. 1,3-Butadiene and isoprene are particularlypreferred.

The diene monomers can optionally be copolymerized with other monomerscontaining ethylenic unsaturation, such as, for example: alfa-olefinscontaining from 2 to 12 carbon atoms (for example ethylene, propylene or1-butene), monovinylarenes containing from 8 to 20 carbon atoms (forexample styrene, 1-vinylnaphthalene or 3-methylstyrene), vinyl esters inwhich the ester group contains from 2 to 8 carbon atoms (for examplevinyl acetate, vinyl propionate or vinyl butanoate), alkyl acrylates andalkyl methacrylates in which the alkyl contains from 1 to 8 carbon atoms(for example ethyl acrylate, methyl acrylate, methyl methacrylate,tert-butyl acrylate or n-butyl acrylate), acrylonitrile, and the like,or mixtures thereof.

Among the epoxidized diene oligomers which are preferred are thosederived from the epoxidation of oligomers of: 1,3-butadiene; isoprene;1,3-butadiene and styrene; 1,3-butadiene and isoprene; isoprene andstyrene; 1,3-butadiene and acrylonitrile; and the like. Epoxidizedoligomers of 1,3-butadiene or of isoprene are particularly preferred.

Epoxidized diene oligomers which may be used in the present inventionare commercially available, for example under the brand name Poly BD®from Elf Atochem. The amount of lubricant may generally range from 5 to70 phr and preferably from 10 to 50 phr.

For the purpose of increasing the rate of crosslinking, an effectiveamount of a condensation catalyst may also be added to the crosslinkablecompositions according to the present invention. This amount may varywithin a wide range, and is generally from 0.01 to 5 parts by weight,preferably from 0.1 to 3 parts by weight, relative to 100 parts byweight of carboxylated elastomeric polymer. The catalyst may be chosenfrom:

-   -   carboxylates of metals such as tin, zinc, zirconium, iron, lead,        cobalt, barium, calcium or manganese, and the like, for example:        dibutyltin dilaurate, dibutyltin diacetate, dioctyltin        dilaurate, stannous acetate, stannous caprylate, lead        naphthenate, zinc caprylate, zinc naphthenate, cobalt        naphthenate, ferrous octanoate, iron 2-ethylhexanoate, and the        like;    -   arylsulphonic acids or derivatives thereof, for example:        p-dodecylbenzenesulphonic acid, tetrapropylbenzenesulphonic        acid, acetyl p-dodecylbenzenesulphonate, 1-naphthalenesulphonic        acid, 2-naphthalenesulphonic acid, acetyl methanesulphonate,        acetyl p-toluenesulphonate, and the like;    -   strong inorganic acids or bases, such as sodium hydroxide,        potassium hydroxide, hydrochloric acid or sulphuric acid, and        the like;    -   amines and alkanolamines, for example ethylamine, dibutylamine,        hexylamine, pyridine or dimethylethanolamine, and the like;    -   oxides or inorganic salts of a metal chosen from Fe, Cu, Sn, Mo        and Ni (as disclosed in the co-pendent European patent        application No. 01-102 664 in the name of the Applicant, which        is incorporated herein by reference), or mixtures thereof.

When an inorganic salt is used, this salt is preferably chosen fromchlorides, bromides, sulphates, nitrates, in anhydrous or hydrated form.

For example, the crosslinking accelerator may be chosen from SnCl₂.2H₂O,CuSO₄.5H₂O, (NH₄)₂Fe(SO₄)₂.6H₂O, NiNO₃.6H₂O and MoO₃, or mixturesthereof (as disclosed in the abovementioned European patent applicationNo. 01-102 664).

The crosslinkable compositions according to the present invention can beprepared by mixing the polymer base and the reinforcing filleroptionally present and the other additives according to techniques knownin the art. The mixing can be carried out, for example, using anopen-mill mixer, or an internal mixer of the type with tangential rotors(Banbury) or interlocking rotors (Intermix), or in continuous mixers ofthe Ko-Kneader (Buss) or co-rotating or counter-rotating twin-screwtype.

During the mixing, the temperature is kept below a predetermined valueso as to avoid premature crosslinking of the composition. To this end,the temperature is generally kept below 170° C., preferably below 150°C., even more preferably below 140° C. As regards the mixing time, thiscan vary within a wide range, depending mainly on the specificcomposition of the mixture, on the presence of any fillers and on thetype of mixer used. In general, a mixing time of more than 90 sec,preferably between 3 and 35 min, is sufficient to obtain a homogeneouscomposition.

In order to optimize the dispersion of the filler while keeping thetemperature below the values indicated above, multi-stage mixingprocesses can also be employed, optionally using a combination ofdifferent mixers arranged in series.

As an alternative to the abovementioned solid-state mixing processes, inorder to improve the dispersion of the components, the crosslinkablecompositions according to the present invention can advantageously beprepared by mixing the reinforcing filler and the other additives, withthe polymer base in the form of an aqueous emulsion or a solution in anorganic solvent. The filler, if present, can be used as it is or in theform of a suspension or dispersion in an aqueous medium. The polymer issubsequently separated from the solvent or from the water by suitablemeans. For example, when a polymer in emulsion is used, the polymer canbe precipitated in the form of particles containing the oily phase andthe filler, if present, can be obtained by adding a coagulant. Acoagulant which can be used in particular is an electrolytic solution,for example an aqueous sodium or potassium silicate solution. Thecoagulation process can be promoted by using a volatile organic solventwhich is then removed by evaporation during precipitation of the filledpolymer. Further details regarding processes of this type for thepreparation of elastomeric compounds are given, for example, in U.S.Pat. No. 3,846,365.

The present invention will now be illustrated in further detail by meansof a number of preparation examples, with reference to:

the attached FIG. 1, which is a view in cross section with partialcutaway of a tyre according to the present invention.

With reference to FIG. 1, a tyre 1 conventionally comprises at least onecarcass ply 2 whose opposite lateral edges are associated withrespective anchoring bead wires 3, each enclosed in a bead 4 definedalong an inner circumferential edge of the tyre, with which the tyreengages on a rim 5 forming part of the wheel of a vehicle.

The association of the carcass ply 2 to the bead wires 3 is usuallycarried out by folding back the opposite side edges of the carcass ply 2around the bead wires 3, so as to form what is known as carcassback-folds.

Alternatively, conventional bead wires 3 may be replaced with a pair ofcircumferentially inextensible annular inserts formed from elongateelements arranged in concentric coils (not shown in FIG. 1) (see, forexample, European patent applications EP-A-0 928 680 and EP-A-0 928702). In this case, the carcass ply 2 is not back-folded around saidannular inserts, the coupling being provided by a second carcass ply(not shown in FIG. 1) applied externally to the first carcass ply.

Along the circumferential development of the carcass ply 2 are appliedone or more belt strips 6, made using metal or textile cords enclosed ina sheet of compound. Outside the carcass ply 2, in respective oppositeside portions of this ply, there is also applied a pair of side walls 7,each of which extends from the bead 4 to a so-called “shoulder” region 8of the tyre, defined by the opposing ends of the belt strips 6. On thebelt strips 6 is circumferentially applied a tread band 9 whose sideedges end at the shoulders 8, joining it to the side walls 7. The treadband 9 externally has a rolling surface 9 a, designed to come intocontact with the ground, in which circumferential grooves 10 can beprovided, intercalated with transverse notches, not shown in theattached figure, which define a plurality of blocks 11 variouslydistributed on said rolling surface 9 a.

The process for producing the tyre according to the present inventioncan be carried out according to techniques and using apparatus known inthe art (see, for example, patents EP 199,064, U.S. Pat. No. 4,872,822and U.S. Pat. No. 4,768,937). More particularly, this process comprisesa stage of manufacturing the green tyre, in which a series ofsemi-finished articles, prepared beforehand and separately from eachother and corresponding to the various parts of the tyre (carcass plies,belt strips, bead wires, fillers, side walls and tread bands) arecombined together using a suitable manufacturing machine.

The green tyre thus obtained is then subjected to the subsequent stagesof moulding and crosslinking. To this end, a vulcanization mould is usedwhich is designed to receive the tyre being processed inside a mouldingcavity having walls which are countermoulded to the outer surface of thetyre when the crosslinking is complete. Alternative processes forproducing a tyre or tyre parts without using semi-finished products aredisclosed, for example, in the abovementioned patent applications EP-A-0928 680 and EP-A-0 928 702.

The green tyre can be moulded by introducing a pressurized fluid intothe space defined by the inner surface of the tyre, so as to press theouter surface of the green tyre against the walls of the mouldingcavity. In one of the moulding methods most widely practised, avulcanization chamber made of elastomeric material, filled with steamand/or another fluid under pressure, is inflated inside the tyre closedinside the moulding cavity. In this way, the green tyre is pushedagainst the inner walls of the moulding cavity, thus obtaining thedesired moulding. Alternatively, the moulding can be carried out withoutan inflatable vulcanization chamber, by providing inside the tyre atoroidal metal support shaped according to the configuration of theinner surface of the tyre to be obtained (see, for example, patent EP242,840). The difference in coefficient of thermal expansion between thetoroidal metal support and the crude elastomeric material is exploitedto achieve an adequate moulding pressure.

At this point, the stage of crosslinking of the crude elastomericmaterial present in the tyre is carried out. To this end, the outer wallof the vulcanization mould is placed in contact with a heating fluid(generally steam) such that the outer wall reaches a maximum temperaturegenerally of between 100° C. and 230° C. Simultaneously, the innersurface of the tyre is brought to the crosslinking temperature using thesame pressurized fluid used to press the tyre against the walls of themoulding cavity, heated to a maximum temperature of between 100 and 250°C. The time required to obtain a satisfactory degree of crosslinkingthroughout the mass of the elastomeric material can vary in generalbetween 3 min and 90 min and depends mainly on the dimensions of thetyre.

The present invention will now be illustrated in further detail by meansof a number of preparation examples.

EXAMPLES 1-6

The epoxidized natural rubber used in the compositions reported in Table1 was prepared in the following manner.

To a solution of natural rubber dissolved in chloroform (5% by weight ofpolymer/volume of solvent) were added, with stirring, variable amountsof peracetic acid depending on the desired degree of epoxidation. Thesolution was brought to a temperature of 40° C. with continued stirring,and left under these conditions for 2 hours. Once the reaction wascomplete, the polymer was precipitated in methanol. In order to removeany residual epoxidizing agents, all the fractions were redissolved inchloroform and precipitated in methanol. The product obtained was driedin an oven at 20° C. under vacuum.

The degree of epoxidation was determined by NMR analysis.

The compositions reported in Table 1 were prepared using an opencylinder mixer., with a mixing time of about 30 minutes, reaching afinal temperature of about 130° C.

The compositions thus prepared were subjected to MDR rheometric analysisusing an MDR rheometer from Monsanto, the tests being carried out at200° C. for 30 minutes, with an oscillation frequency of 1.66 Hz (100oscillations per minute) and an oscillation amplitude of ±0.5°. Table 1gives the ML and MH values and the T₉₀ value, in which ML is the minimumtorque, MH is the maximum torque and T₉₀ is the time corresponding to atorque value equal to ML+0.9 (MH−ML). The mechanical properties(according to ISO standard 37) and the hardness in degrees IRHD(according to ISO standard 48) were measured on samples of theabovementioned compositions crosslinked at 200° C. for 15 min. Theresults are given in Table 1. TABLE 1 Example 1 2 3 4 5* 6* NipolEP ® 1072 80 80 80 80 80 80 ENR 2% 20 ENR4% 20 ENR7% 20 ENR9.5% 20Epoxyprene ® 25% 20 Epoxyprene ® 50% 20 Zeosil ® 1165 MP 70 70 70 70 7070 PARAPLEX ® G-60 30 30 30 30 30 30 Vulcanox ® 4020 1 1 1 1 1 1SANTOFLEX ® 13 2 2 2 2 2 2 Poliplastol ® 3 3 3 3 3 3 ML 30 min/200° C.4.1 4.2 3.24 6.4 5.85 8.36 MH 30 min/200° C. 30.3 31.5 24.5 30.1 23.125.9 T90 30 min/200° C. 4.35 4.4 3.8 4.7 5.45 5.48 100% load (MPa) 3.794.67 4.22 4.21 6.94 10.52 300% load (MPa) 9.52 11.33 10.77 10.12 Stressat break 10.9 12 12 11.8 12.5 12.8 (MPa) Elongation at 389 354 379 405208 130 break IRHD hardness at 79 78 78 76 80 80 23° C. (degrees) IRHDhardness at 100° C. 70 72 70 72 76 79 (degrees)*comparative Nipol EP ® 1072: acrylonitrile-butadiene-carboxylatemonomer terpolymer containing 28% by weight of acrylonitrile and 7.5% byweight of carboxylic groups (Nippon Zeon);ENR: epoxidized natural rubber with degrees of epoxidation ranging from2 mol % to 9.5 mol %, prepared as described above.Epoxyprene ® ENR 50%: epoxidized natural rubber containing 50 mol % ofepoxide groups and having an average molecular weight of greater than100,000 (produced by Guthrie Symington Ltd).Epoxyprene ® ENR 25%: epoxidized natural rubber containing 25 mol % ofepoxide groups and having an average molecular weight of greater than100,000 (produced by Guthrie Symington Ltd).Zeosil ® 1165 MP: precipitated silica with a BET surface area equal toabout 165 m²/g (Rhône-Poulenc)Paraplex ® G-60: epoxidized soybean oil having: freezing temperature =5° C., average molecular weight = 1000 and epoxide-equivalent weight =210 (C.P. Hall);Vulcanox ® 4020: tetramethylquinoline (Bayer)Santoflex ® 13: anti-ageing additive 6PPD (Monsanto).Poliplastol ®: Zn salts of fatty acids (Great Lakes)

EXAMPLES 7-11

The epoxidized polybutadiene (BR) used in the blends indicated in Table2 was prepared in the following manner.

To a solution of polybutadiene (Europrene® Neocis BR40) dissolved inchloroform (5% by weight of polymer/volume of solvent) was added, withstirring, amounts of peracetic acid varying according to the desireddegree of epoxidation. The solution was brought to a temperature of 40°C. with continued stirring, and maintained under these conditions for 2hours. The epoxidation reaction was carried out in a 5 litre glassreactor equipped with a heating jacket, a sealing stopper and a refluxcondenser for the solvent vapours. Once the reaction was complete, thepolymer was precipitated in methanol. In order to remove any residualepoxidizing agent, all the fractions were redissolved in chloroform andprecipitated in methanol. The product obtained was dried in an oven at20° C. under vacuum.

The degree of epoxidation was determined by NMR analysis. Thecompositions given in Table 2 were prepared using an open cylindermixer, with a mixing time of about 30 minutes, reaching a finaltemperature of about 130° C.

The compositions were then subjected to MDR rheometric analysis usingthe same rheometer and under the same conditions as those of Examples1-6. The optimum crosslinking conditions were determined on the basis ofthe rheometric analysis.

The mechanical properties (according to ISO standard 37) and thehardness in degrees IRHD at 23° C. and at 100° C. (according to ISOstandard 48) were measured on samples of the abovementioned compositionscrosslinked under the optimum conditions. The dynamic elastic propertieswere also evaluated, of which the dynamic elastic modulus (E′) measuredat 23° C. and at 70° C. by a dynamic Instron device intraction-compression, according to the following methods, are reported.A sample of the crosslinkined material in cylindrical form (length=25mm; diameter=14 mm), pre-loaded in compression up to a longitudinaldeformation of 10% relative to the initial length, and keept at a presettemperature (23° C. or 70° C.) throughout the test, was subjected to adynamic sinusoidal deformation of amplitude ±3.33% relative to thelength under pre-loading, with a frequency of 100 Hz. The results aregiven in Table 3.

The dynamic elastic properties are expressed in terms of E′ and tandelta (loss factor) at 23° C. and at 70° C. As is known, the tan deltavalue is calculated as the ratio between the viscous modulus (E″) andthe elastic modulus (E′), both of which are determined by the dynamicmeasurements mentioned above. TABLE 2 Example 7 8 9 10 11 NipolEP ® 1072 80 80 80 80 80 EBR 3% 20 EBR 2.2% 20 EBR 6.4% 20 EBR 7.4% 20EBR 11.4% 20 PARAPLEX ® G-60 30 30 30 30 30 Zeosil ® 1165 MP 70 70 70 7070 Vulcanox ® 4020 1 1 1 1 1 SANTOFLEX ® 13 2 2 2 2 2 Poliplastol ® 3 33 3 3EBR: epoxidized polybutadiene with degrees of epoxidation ranging from2.2 mol % to 11.4 mol %, prepared as described above.

TABLE 3 Example 7 8 9 10 11 100% load (MPa) 2.5 2.44 3.14 4.31 5.36 300%load (MPa) 8.9 8.86 10.94 13.86 17.54 Stress at break 14.8 14.81 15.4618.74 15.93 (MPa) Elongation at 499 498.8 460.9 447.9 294.4 break IRHDhardness at 80 80.2 81.4 85.5 84.9 23° C. (degrees) IRHD hardness at 7070 77.2 79.1 79.5 100° C. (degrees) E′ 23° C. 15.6 15.6 19.48 20.4821.73 E′ 70° C. 8.98 8.98 11.84 12.94 13.83 tan delta 23° C. 0.382 0.3820.366 0.341 0.321 tan delta 70° C. 0.218 0.218 0.208 0.184 0.172 DINabrasion 90 89.7 90.7 93.2 98.3

1. Process for producing tyres for vehicle wheels, said process comprising the following stages: manufacturing a green tyre comprising at least one crosslinkable elastomeric material; subjecting the green tyre to moulding in a mould cavity defined in a vulcanization mould; crosslinking the elastomeric material by heating the tyre to a predetermined temperature and for a predetermined time; characterized in that the crosslinkable elastomeric material comprises: (a) an elastomeric polymer containing carboxylic, groups, and (b) an epoxidized elastomeric polymer containing from 0.1 mol % to 20 mol % of epoxide groups relative to the total number of moles of monomers present in the polymer, in which said crosslinking stage is carried out in the substantial absence of additional crosslinking agents.
 2. Process according to claim 1, in which the crosslinking stage is carried out by heating the crosslinkable elastomeric material to a temperature of at least 120° C. for a time of at least 3 minutes.
 3. Process according to claim 2, in which the crosslinking stage is carried out by heating the crosslinkable elastomeric material to a temperature of from 130° C. to 230° C. for a time of from 5 to 90 minutes.
 4. Process according to any one of the preceding claims, in which the elastomeric material also comprises a reinforcing filler.
 5. Process according to claim 4, in which the reinforcing filler is present in an amount of between 10 and 120 phr.
 6. Process according to claim 5, in which the reinforcing filler is present in an amount of between 30 and 100 phr.
 7. Process according to any one of the preceding claims, in which said crosslinkable elastomeric material comprises a lubricant.
 8. Process according to claim 7, in which said lubricant is an epoxidized lubricant containing epoxide groups located internally on the molecule.
 9. Process according to claim 8, in which said epoxidized lubricant has an epoxide-equivalent weight of between 40 and 2,000.
 10. Process according to any one of claims 7 to 9, in which said lubricant is an epoxidized oil.
 11. Process according to any one of claims 7 to 9, in which the epoxidized lubricant is an epoxidized diene oligomer.
 12. Process according to any one of the preceding claims, in which the elastomeric polymer containing carboxylic groups is a homopolymer or copolymer containing at least 0.1 mol % of carboxylic groups relative to the total number of moles of monomers present in the polymer.
 13. Process according to claim 12, in which the carboxylated elastomeric polymer contains from 1 mol % to 30 mol % of carboxylic groups relative to the total number of moles of monomers present in the polymer.
 14. Process according to claim 13, in which the carboxylated elastomeric polymer contains from 2 mol % to 10 mol % of carboxylic groups relative to the total number of moles of monomers present in the polymer.
 15. Process according to any one of the preceding claims, in which the carboxylated elastomeric polymer has an average molecular weight of between 2,000 and 1,000,000.
 16. Process according to claim 15, in which the carboxylated elastomeric polymer has an average molecular weight of between 50,000 and 500,000.
 17. Process according to any one of the preceding claims, in which the carboxylated elastomeric polymer is obtained by (co)polymerization of one or more conjugated diene monomers, optionally mixed with monovinylarenes and/or polar comonomers, followed by carboxylation.
 18. Process according to any one of claims 1 to 16, in which the carboxylated elastomeric polymer is obtained by copolymerization of a conjugated diene, optionally mixed with monovinylarenes and/or polar comonomers, and an olefinic monomer containing one or more carboxylic groups or a derivative thereof.
 19. Process according to any one of claims 1 to 16, in which the carboxylated elastomeric polymer is obtained by copolymerization of one or more monoolefins with an olefinic comonomer containing one or more carboxylic groups, or derivatives thereof.
 20. Process according to any one of the preceding claims, in which the epoxidized elastomeric polymer contains from 0.5 mol % to 15 mol % of epoxide groups relative to the total number of moles of monomers present in the polymer.
 21. Process according to claim 20, in which the epoxidized elastomeric polymer contains from 1 mol % to 10 mol % of epoxide groups relative to the total number of moles of monomers present in the polymer.
 22. Process according to any one of the preceding claims, in which the epoxidized elastomeric polymer containing epoxide groups has a glass transition temperature (Tg) of less than 23° C.
 23. Process according to any one of the preceding claims, in which the epoxidized elastomeric polymer has an average molecular weight of between 2,000 and 1,000,000.
 24. Process according to claim 23, in which the epoxidized elastomeric polymer has an average molecular weight of between 50,000 and 500,000.
 25. Process according to any one of the preceding claims, in which the epoxidized elastomeric polymer is an epoxidized diene homopolymer or copolymer derived from one or more conjugated diene monomers, optionally copolymerized with monovinylarenes and/or polar comonomers.
 26. Process according to claim 25, in which the epoxidized elastomeric polymer is epoxidized natural rubber.
 27. Process according to any one of claims 1 to 24, in which the epoxidized elastomeric polymer is obtained by copolymerization of a conjugated diene, optionally mixed with monovinylarenes and/or polar comonomers, and an olefinic monomer containing one or more epoxide groups.
 28. Process according to any one of claims 1 to 24, in which the epoxidized elastomeric polymer is a copolymer of one or more monoolefins with an olefinic comonomer containing one or more epoxide groups.
 29. Tyre for vehicles wheels, comprising one or more components made of crosslinked elastomeric material, characterized in that at least one of said components comprises, as crosslinked elastomeric material, an elastomeric polymer containing carboxylic groups and an epoxidized elastomeric polymer containing from 0.1 mol % to 20 mol % of epoxide groups relative to the total number of moles of monomers present in the polymer, said polymers being crosslinked in the substantial absence of additional crosslinking agents.
 30. Tyre according to claim 29, in which said crosslinked elastomeric material also comprises a reinforcing filler.
 31. Tyre according to claim 30, in which the reinforcing filler is present in an amount of between 10 and 120 phr.
 32. Tyre according to claim 31, in which the reinforcing filler is present in an amount of between 30 and 100 phr.
 33. Tyre according to any one of claims 29 to 32, in which said crosslinked elastomeric material also comprises a lubricant.
 34. Tyre according to claim 33, in which said lubricant is defined according to any one of claims 7 to
 11. 35. Tyre according to any one of claims 29 to 34, in which the elastomeric polymer containing carboxylic groups is defined according to any one of claims 12 to
 19. 36. Tyre according to any one of claims 29 to 35, in which the epoxidized elastomeric polymer is defined according to any one of claims 20 to
 28. 37. Tyre for vehicles, comprising a belt structure extended coaxially around a carcass structure and a tread band extended coaxially around the belt structure and having an external rolling surface which is intended to come into contact with the ground, characterized in that said tread band comprises an elastomeric polymer containing carboxylic groups and an epoxidized elastomeric polymer containing from 0.1 mol % to 20 mol % of epoxide groups relative to the total number of moles of monomers present in the polymer, said polymers being crosslinked in the substantial absence of additional crosslinking agents.
 38. Tyre according to claim 37, in which the tread band also comprises a reinforcing filler.
 39. Tyre according to claim 38, in which the reinforcing filler is present in an amount of between 10 and 120 phr.
 40. Tyre according to claim 39, in which the reinforcing filler is present in an amount of between 30 and 100 phr.
 41. Tyre according to any one of claims 37 to 40, in which said crosslinked elastomeric material also comprises a lubricant.
 42. Tyre according to claim 41, in which said lubricant is defined according to any one of claims 7 to
 11. 43. Tyre according to any one of claims 37 to 42, in which the elastomeric polymer containing carboxylic groups is defined according to any one of claims 12 to
 19. 44. Tyre according to any one of claims 37 to 43, in which the epoxidized elastomeric polymer is defined according to any one of claims 20 to
 28. 45. Crosslinkable elastomeric composition comprising: (a) an elastomeric polymer containing carboxylic groups; and (b) an epoxidized elastomeric polymer containing from 0.1 mol % to 20 mol % of epoxide groups relative to the total number of moles of monomers present in the polymer; said composition being crosslinkable in the substantial absence of additional crosslinking agents.
 46. Crosslinkable elastomeric composition according to claim 45, also comprising a reinforcing filler.
 47. Composition according to claim 46, in which the reinforcing filler is present in an amount of between 10 and 120 phr.
 48. Composition according to claim 47, in which the reinforcing filler is present in an amount of between 30 and 100 phr.
 49. Composition according to any one of claims 45 to 48, also comprising a lubricant.
 50. Composition according to claim 49, in which said lubricant is an epoxidized lubricant containing epoxide groups located internally on the molecule.
 51. Composition according to claim 50, in which the epoxidized lubricant has an epoxide-equivalent weight of between 40 and 2,000.
 52. Composition according to claim 51, in which the epoxidized lubricant has an epoxide-equivalent weight of between 50 and 1,500.
 53. Composition according to claim 52, in which the epoxidized lubricant has an epoxide-equivalent weight of between 100 and 1,000.
 54. Composition according to any one of claims 49 to 53, in which the epoxidized lubricant is an epoxidized oil.
 55. Composition according to claim 54, in which the epoxidized oil has a freezing temperature of less than 23° C.
 56. Composition according to any one of claims 49 to 53, in which the epoxidized lubricant is an epoxidized diene oligomer.
 57. Composition according to claim 56, in which the epoxidized diene oligomer has an average molecular weight of between 500 and 10,000.
 58. Composition according to claim 57, in which the epoxidized diene oligomer has an average molecular weight of between 1,000 and 8,000.
 59. Composition according to any one of claims 56 to 58, in which the epoxidized diene oligomer is an epoxidized oligomer of 1,3-butadiene or isoprene, or blends thereof.
 60. Composition according to any one of claims 45 to 59, in which the elastomeric polymer containing carboxylic groups is a homopolymer or copolymer containing at least 0.1 mol % of carboxylic groups relative to the total number of moles of monomers present in the polymer.
 61. Composition according to claim 60, in which the carboxylated elastomeric polymer contains from 1 mol % to 30 mol % of carboxylic groups relative to the total number of moles of monomers present in the polymer.
 62. Composition according to any one of claims 45 to 61, in which the carboxylated elastomeric polymer has an average molecular weight of between 2,000 and 1,000,000.
 63. Composition according to claim 62, in which the carboxylated elastomeric polymer has an average molecular weight of between 50,000 and 500,000.
 64. Composition according to any one of claims 45 to 63, in which the carboxylated elastomeric polymer is obtained by (co)polymerization of one or more conjugated diene monomers, optionally mixed with monovinylarenes and/or polar comonomers, followed by carboxylation.
 65. Composition according to any one of claims 45 to 63, in which the carboxylated elastomeric polymer is obtained by copolymerization of a conjugated diene, optionally mixed with monovinylarenes and/or polar comonomers, and an olefinic polymer containing one or more carboxylic groups, or a derivative thereof.
 66. Composition according to any one of claims 45 to 63, in which the carboxylated elastomeric polymer is obtained by copolymerization of one or more monoolefins with an olefinic comonomer containing one or more carboxylic groups, or derivatives thereof.
 67. Composition according to any one of claims 45 to 66, in which the epoxidized elastomeric polymer contains from 0.5 mol % to 15 mol % of epoxide groups relative to the total number of moles of monomers present in the polymer.
 68. Composition according to claim 67, in which the epoxidized elastomeric polymer contains from 1 mol % to 10 mol % of epoxide groups relative to the total number of moles of monomers present in the polymer.
 69. Composition according to any one of claims 45 to 68, in which the epoxidized elastomeric polymer containing epoxide groups has a glass transition temperature (Tg) of less than 23° C.
 70. Composition according to any one of claims 45 to 69, in which the epoxidized elastomeric polymer has an average molecular weight of between 2,000 and 1,000,000.
 71. Composition according to claim 70, in which the epoxidized elastomeric polymer has an average molecular weight of between 50,000 and 500,000.
 72. Composition according to any one of claims 45 to 71, in which the epoxidized elastomeric polymer is an epoxidized diene homopolymer or copolymer derived from one or more conjugated diene monomers, optionally copolymerized with monovinylarenes and/or polar comonomers.
 73. Composition according to claim 72, in which the epoxidized elastomeric polymer is epoxidized natural rubber.
 74. Composition according to any one of claims 45 to 71, in which the epoxidized elastomeric polymer is a copolymer of one or more monoolefins with an olefinic comonomer containing one or more epoxide groups.
 75. Composition according to any one of claims 45 to 71, in which the epoxidized elastomeric polymer is obtained by copolymerization of a conjugated diene, optionally blended with monovinylarenes and/or polar comonomers, and an olefinic monomer containing one or more epoxide groups.
 76. Crosslinked elastomeric manufactured product obtained by crosslinking a composition according to any one of claims 45 to
 75. 